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Erschienen in:
23.12.2021 | Test Yourself: Answer
Painful suprapatellar mass
Erschienen in: Skeletal Radiology | Ausgabe 7/2022
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Ultrasound examination of the left knee demonstrated a 11 × 11 × 5 mm well-circumscribed hypoechoic subcutaneous mass with central tiny cystic space superficial to the quadriceps tendon (Fig. 1a). Spectral Doppler showed marked vascularity and ‘vascular stalk sign’. Arterial flow and to a lesser degree venous flow were demonstrated (Fig. 1b). The mass was non-compressible and very tender during assessment. On magnetic resonance imaging (MRI), it was T1W hypointense, T2W hyperintense and avidly enhancing (Fig. 2a-c). Internal cystic change was observed. Full-thickness sagittal maximum-intensity-projection (MIP) image from the time-resolved MR angiography (MRA) showed early marked arterial enhancement (Fig. 3). Imaging features were suggestive of glomus tumor. Surgical excision of the mass was performed, and histological diagnosis of glomus tumor was confirmed (Fig. 4). Knee pain had dissipated on follow-up.
Fig 1
(a, b): Ultrasound images of the left knee. a Greyscale ultrasound shows a 1.1 × 1.1 × 0.5 cm well circumscribed hypoechoic subcutaneous mass (arrow) with central tiny cystic space at the anterior knee superficial to quadriceps tendon (asterisk). b Doppler examination demonstrates internal hypervascularity, prominent vessel connecting the lesion (arrow) to adjacent soft tissue termed ‘vascular stalk sign’ (arrowhead). Spectral doppler demonstrates both arterial and to a lesser degree venous flow.
Fig 2
(a–c): MRI examination of the left knee. a Sagittal T1-weighted MRI image shows a 1.1 cm homogenous hypointense well circumscribed subcutaneous mass (arrow) at the pre-patellar region of left knee. b Sagittal T2-weighted, fat-saturated MRI image shows that the mass (arrow) is T2W hyperintense with tiny internal cystic changes. Mild periphery subcutaneous edema is noted. c Sagittal T1-weighted, fat-saturated post-contrast MRI image shows vivid homogenous enhancement of the mass (arrow).
Fig. 3
Full-thickness sagittal maximum-intensity-projection (MIP) image from the time-resolved MR angiography (MRA) shows early and marked enhancement of the mass (arrow) in the arterial phase
Fig 4
(a–d) Glomus tumor histopathology. a Haematoxylin and eosin stain shows characteristic round cells with round nuclei and moderate amount of eosinophilic cytoplasm traversed by capillary sized vessels (arrow). Immunohistochemical stains were positive for b calponin, c actin and d h-caldesmon, as is typically seen in glomus tumors.
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